REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	$ 190,439	$ 162,215	$ 367,615	$ 316,402
Platform Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	172,052	147,148	333,671	287,765
Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	$ 18,387	$ 15,067	$ 33,944	$ 28,637